This research concerns the development of substance use (alcohol, tobacco, or other drugs). One of the important empirical issues for this topic is identification of the risk factors during each age period that are associated with greater or lesser likelihood of subsequent substance use. No one study can cover all the risk variables, age periods, subject samples, and substance use outcomes that are of theoretical or practical importance, but advanced meta-analysis techniques can be used to conduct a detailed analysis and synthesis of empirical evidence across the full body of existing research. In a previous meta-analysis, data were coded from 1,557 reports of 215 longitudinal studies to generate a database of approximately 14,000 correlational effect sizes representing predictive relationships between risk variables and alcohol, tobacco, and drug use across a wide age range. The project proposed here will, first, update and extend that database to include recent research reports and to code correlations among risk variables and among outcome variables along with the risk- outcome correlations that were the focus of the earlier work. Second, further statistical analyses will be conducted to differentiate and synthesize the body of empirical research findings in relation to the following issues: 1. The categorization of antecedent risk variables into groups (factors) that are conceptually and empirically related to each other at different age periods. 2. The relative independent strength of association of the different categories of antecedent risk variables with subsequent substance use, and how those associations vary by life stage and type of substance used. Particular attention will be paid to the convergence of empirical data with theoretical formulations about associations between risk factors and substance use. 3. The comorbidity of substance use and other problem behaviors at various age periods, e.g., the extent of co-occurrence of substance use with aggressive behavior, crime, and mental illness. 4. The relationship of early tobacco, alcohol, or marijuana use (gateway drugs) to subsequent substance use and the related issue of age of onset of first substance use.